A monochromic image is composed of one color (or values of one color). The term monochrome comes from the Ancient Greek: μονόχρωμος, romanized: monochromos, lit.'having one color'.
A monochromatic object or image reflects colors in shades of limited colors or hues. Images using only shades of grey (with or without black or white) are called grayscale or black-and-white. However, scientifically speaking, monochromatic light refers to visible light of a narrow band of wavelengths (see spectral color).
Of an image, the term monochrome is usually taken to mean the same as black and white or, more likely, grayscale, but may also be used to refer to other combinations containing only tones of a single color, such as green-and-white or green-and-red. It may also refer to sepia displaying tones from light tan to dark brown or cyanotype ('blueprint') images, and early photographic methods such as daguerreotypes, ambrotypes, and tintypes, each of which may be used to produce a monochromatic image.
In computing, monochrome has two meanings:
A monochrome computer display is able to display only a single color, often green, amber, red or white, and often also shades of that color.
In film photography, monochrome is typically the use of black-and-white film.Originally, all photography was done in monochrome. Although color photography was possible even in the late 19th century, easily used color films, such as Kodachrome, were not available until the mid-1930s.
In digital photography, monochrome is the capture of only shades of black by the sensor, or by post-processing a color image to present only the perceived brightness by combining the values of multiple channels (usually red, blue, and green). The weighting of individual channels may be selected to achieve a desired artistic effect; if only the red channel is selected by the weighting then the effect will be similar to that of using a red filter on panchromatic film. If the red channel is eliminated and the green and blue combined then the effect will be similar to that of orthochromatic film or the use of a cyan filter on panchromatic film. The selection of weighting thus allows a wide range of artistic expression in the final monochromatic image.
For production of an anaglyph image the original color stereogram source may first be reduced to monochrome in order to simplify the rendering of the image. This is sometimes required in cases where a color image would render in a confusing manner given the colors and patterns present in the source image and the selection filters used (typically red and its complement, cyan).
In physics, monochromatic light is electromagnetic radiation of a single frequency. In the context of physics, no source of electromagnetic radiation is purely monochromatic, since that would require a wave of infinite duration as a consequence of the Fourier transform's localization property (cf. spectral coherence). Even very controlled sources such as lasers operate in a range of frequencies (known as the spectral linewidth). In practice, filtered light, diffraction grating separated light and laser light are all routinely referred to as monochromatic. Often light sources can be compared and one be labeled as “more monochromatic” (in a similar usage as monodispersity). A device which isolates a narrow band of frequencies from a broader-bandwidth source is called a monochromator, even though the bandwidth is often explicitly specified, and thus a collection of frequencies is understood.
|Look up monochrome in Wiktionary, the free dictionary.|
You want to use colors in a graph with ggplot2.
The default colors in ggplot2 can be difficult to distinguish from one another because they have equal luminance. They are also not friendly for colorblind viewers.
A good general-purpose solution is to just use the colorblind-friendly palette below.
These two data sets will be used to generate the graphs below.
The colors of lines and points can be set directly using
colour='red', replacing “red” with a color name. The colors of filled objects, like bars, can be set using
If you want to use anything other than very basic colors, it may be easier to use hexadecimal codes for colors, like
'#FF6699'. (See the hexadecimal color chart below.)
Instead of changing colors globally, you can map variables to colors – in other words, make the color conditional on a variable, by putting it inside an
These are color-blind-friendly palettes, one with gray, and one with black.
To use with ggplot2, it is possible to store the palette in a variable, then use it later.
This palette is from http://jfly.iam.u-tokyo.ac.jp/color/:
By default, the colors for discrete scales are evenly spaced around a HSL color circle. For example, if there are two colors, then they will be selected from opposite points on the circle; if there are three colors, they will be 120° apart on the color circle; and so on.The colors used for different numbers of levels are shown here:
The default color selection uses
scale_colour_hue(). For example, adding those commands is redundant in these cases:
scale_colour_hue() were redundant above, they can be used when you want to make changes from the default, like changing the luminance or chromaticity.
This is a chart of colors with luminance=45:
You can also use other color scales, such as ones taken from the RColorBrewer package. See the chart of RColorBrewer palettes below. See the scale section here for more information.
Finally, you can define your own set of colors with
scale_fill_manual(). See the hexadecimal code chart below for help choosing specific colors.
See the scale section here for more information.
Colors can specified as a hexadecimal RGB triplet, such as
'#0066CC'. The first two digits are the level of red, the next two green, and the last two blue. The value for each ranges from 00 to FF in hexadecimal (base-16) notation, which is equivalent to 0 and 255 in base-10. For example, in the table below, “#FFFFFF” is white and “#990000” is a deep red.
(Color chart is from http://www.visibone.com)